In order to pass the Q101 automotive quality specification a power semiconductor device must pass the autoclave test. The autoclave test involves simultaneously subjecting devices to at least 121° C. temperature, at least 100% relative humidity and at least 2 bars (15 PSIG) pressure for at least 96 hrs. The test is designed to evaluate the moisture resistance integrity of non-hermetic packages.
Referring to FIGS. 1A-1C, a package 10 according to the prior art includes a conductive can 12, and a power semiconductor die 14. Can 12 is typically formed with an electrically conductive material such as copper or a copper-based alloy, and may be coated with silver, gold or the like. Die 14 may be a vertical conduction type power semiconductor MOSFET having its drain electrode 16 electrically and mechanically attached to an interior surface of can 12 by a conductive adhesive 18 such as solder or a conductive epoxy (e.g. silver loaded epoxy). Source electrode 20, and gate electrode 22 of die 14 (which are disposed on a surface opposite to the drain electrode) each includes a solderable body which facilitates its direct connection to a respective conductive pad of a circuit board by a conductive adhesive (e.g. solder or conductive epoxy). Note that die 14 further includes passivation body 30 which partially covers source electrode 20 and gate electrode 22, but includes openings to allow access at least to the solderable portions thereof for electrical connection. Note that passivation body 30 may be comprised of a stack of two different passivation materials. In package 10, conductive can 12 includes web portion 13 (to which die 14 is electrically and mechanically connected), wall 15 surrounding web portion 13, and two oppositely disposed rails 32 extending from wall 15 each configured for connection to a respective conductive pad on a circuit board. Die 14 is spaced from wall 13 of can 12; i.e. wall 13 surrounds die 14.
In a package according to the prior art, source electrode 20, and gate electrode 22 may be soldered down by the user. Specifically, the user applies solder to, for example, the pads of a circuit board, and the electrodes of the die are attached to the pads by the solder so placed.
A package as described above is generally shown in U.S. Pat. No. 6,624,522 and also in U.S. patent application Ser. No. 11/378,607 the entire contents of which are incorporated by reference. Also, the assignee of the present application sells packages generally shown by FIGS. 1A-1C herein under the trademark DirectFET.